The nasal mucosa is the first internal surface to encounter aeroallergens, airborne pathogens, and airborne toxins. Analysis of nasal responses will likely provide insights into normal host defense mechanisms. Provocation of human and guinea pig nasal mucosa stimulates protein secretion. Analysis of the components of these secretions has revealed new insights into the source of these secretions as well as possible mechanisms for the pharmacologic control of secretion. Histamine was found to primarily cause increased vascular permeability as reflected in relative enrichment of nasal secretions with albumin, nonsecretory IgA (NS-IgA), and IgG. These effects were inhibited with an H-1 antihistamine but not by atropine. Methacholine caused selective glandular secretion as reflected in increases in total protein, secretory IgA (sIgA), lysozyme, lactoferrin, albumin, and IgG, but no relative enrichment of any of these proteins. Methacholine effects were inhibited by atropine. Hot, spicy foods may cause rhinorrhea in sensitive subjects. Gustatory rhinitis was found to involve an atropine-inhibitable muscarinic pathway and both symptoms and secretory responses could be prevented by pretreatment with atropine.